Method of working sheet



March 10, 1964 N. H. PoLAKowsKl METHOD OF WORKING SHEET, STRIP AND SIMILR MATERIALS Filed June 26, 1961 JNVENTOR. I Unfalls f1', Pola' kowskz @figs United States Patent O 3,123,893 METl-IUD F V/GRKING SHEET, ETRE? AND SHMHJAR MATERlAlLS Natalie H. Polalrowski, :500 Kin Court, Wilmette, lll. Filed .lune 2.6, i961, Ser. No. 119,389 1i) Claims. (Cl. 29-13) The present invention relates to the working of metals and more particularly relates to a process whereby the metal is given a substantial reduction in thickness and is, at the same time, increased in Width to a point beyond heretofore obtainable limits.

In the processing of sheet material it is well known that practical upper and lower limits exist with regard to the width and gage to which a sheet can be rolled. Wide sheet and strip mills are extremely expensive, and very few are capable of handling sheet over about eight feet wide. Mills which are capable of rolling sheet or strip of these extreme Widths are, however, ill-suited for reducing these sheets to relatively thin gages. For full-width sheets the practical lower thickness limit for such mills is about .025 to .040 inch. Gages as thin as .010 or less are unattainable unless the cumbersome pack-rolling method is used.

Problems arise in the manufacture of certain of the rarer metals which, while extremely important for a variety of purposes, are nevertheless processed in relatively small quantities. It is, therefore, highly uneconomical and frequently impractical to employ large rolling mills even if such mills were capable of producing sheet of the desired width and gage. Furthermore, it is often advantageous to heat certain refractory metals such as molybdenum or tungsten during working operations and conventional strip mills are impractical for such purposes since the metal will rapidly lose heat, particularly when it is thin.

It is, therefore, an object of this invention to provide an improved method for the Working of sheet, strip and similar material which will enable economic production of wide, thin material even where relatively small amounts of the material are to be processed.

It is a further object of this invention to eliminate the disadvantages present with regard to existing rolling mills particularly when considering the limitations of these mills regarding the maximum width and minimum gage to which the materials can be processed.

It is an additional object of this invention to provide an improved method suitable for preparing wide, thin sheets of metals which are processed in rather small quantities.

It is an additional object of this invention to provide a method of working sheet metal which is peculiarly adaptable for pre-heating of the material to be worked to elevated temperatures whereby the working of the metal is facilitated.

These and other objects of this invention will appear hereinafter, and for purposes of illustration, but not of limitation, specific embodiments of this invention are shown in the accompanying drawing in which- FIGURE 1 is a side view, partly in section, of the assembly which characterizes the present invention, the assembly including the material to be worked;

FIGURE 2 is a cross-sectional View of an assembly of the type shown in FIGURE l;

FIGURE 3 is a side view, partly in section, of the assembly of the type described as it appears when being drawn through a die;

FIGURE 4 is a side View, partly in section, of the assembly as it appears when being extruded through a die;

FIGURE 5 is a detail cross-sectional View of the product obtained when dissimilar metals are assembled and lrespect to the scroll.

gg, worked in accordance with the practice of this invention; and

FlGURE 6 is a side View, partly in section, ot assembly adapted to be sealed for working in a vacuum.

The present invention generally relates to a process for the working of metallic sheet, strip and similar material wherein the material is wrapped about a core and a case is provided to hold the material in a tightly wrapped state with respect to the core. The assembly, comprising the encasing means, the material and the core, is then worked whereby the outer diameter of the assembly is reduced, this resulting in the assembly becoming longer, and the sheet wrapped thereon, thinner. It will be apparent when considering the disclosure that by continuing the working steps the metal can be reduced to an extremely thin gage and, at the same time, the width of the material will be constantly increasing, thus enabling the production of wide, thin sheet beyond limits heretofore obtainable. The working may be carried out by several known methods including drawing and extruding.

The assemblies of this invention are readily adaptable for pre-heating to a desired working temperature even where extremely thin sheet is evolved. Thus, the compact assembly of this invention will not permit rapid dissipation of the heat, and will remain Within a desired working temperature range for an extended period, allowing a sufllcient time for working.

Referring to the accompanying drawings, FlGURES 1 and 2 illustrate an assembly lll comprising a core or mandrel l2 about which is tightly wrapped a scroll of sheet material 14 which is to be worked. The scroll of material is fixed in position about the core by glueing or welding the exposed end of the scroll to the layer of material immediately beneath. A case le is provided for holding the material 11.4 in position about the mandrel. The end i8 of the mandrel and the end 2l) of the case extend beyond the end of the material le to provide an open space which can be swaged to permit gripping for a drawing operation. A dummy block 22 composed of a readily deformable metal such as copper or soft steel may be provided within the open space near the ends i8 and 20 to eliminate or reduce undesirable end distortions in the material lll during the working operation. A similar annular dummy block (not shown) can also be fitted at the rear end of the assembly between core l2 and casing 16, adjacent to scroll i4.

Grooves 23 may be formed in the case 16 in order to facilitate removal of the case after completion of the working step. The presence of these notches or grooves 23 will tend to cause the case to crack with the aid of a prying force. Two parallel grooves or notches may be provided in order to open the case by pulling out the tongue of metal between the grooves. Other methods of removing the case are also contemplated, such as removal by chemically attacking the case metal with a chemical which will attack the case preferentially with After removing the case, the reduced sheet may be unwrapped from the core, or the core may be stretched plastically after annealin to cause it to contract radially and so separate from scroll ld. Additionally, a passage could be initially formed in the core and a chemical reagent or electrolyte passed therethrough for preferential destruction of the core.

The case 16 is slipped about the core and wrapped sheet and will, of course, be relatively loosely fit with respect thereto. The operation of the invention is carried out by swaging the end of the assembly and pulling the assembly through a drawing die or the like 24, shown in FIGURE 3. The first draw will reduce the case le and cause it to adhere snugly to the scroll 14. It will be apparent that the drawing of the assembly through one or more dies will cause a decrease in the gage of the material and will also cause the material together with the case to elongate in the drawing direction. Since this elongation is in the direction of the original width of the material, a wider sheet is thus produced. In the early stages of drawing the successive drafts should be rather light since only the case and core are available for gripping and force transmittal. After the early stages are completed the end of the assembly may be cropped off and, after swaging, the material will also become part of the ripping portion, thus providing a larger crosssection for transmitting the drawing forces.

FIGURE 4 illustrates the adaptation of this invention to working by hydrostatic extrusion. Thus, a container 26, provided with a ram 28 and uid 30 is adapted to force the assembly through the throat of the die 31 for reduction in the manner heretofore described. The invention can also be practiced by using conventional rather than hydrostatic extrusion.

FIGURE 5 illustrates material 14 which is comprised of a rst strip 32 and a second strip 34 of dissimilar metals. The material 14 thus comprises a scroll of bimetallic material, the material being welded at one interface 36 and free for unwrapping at the other interface 38. In order to produce a bimetallic strip of this type one side of each strip is thoroughly cleaned as by degreasing, etching, etc., and these faces are brought into contact, after which the composite is wrapped around a mandrel in scroll form as above described. After encasing the composite and during the working of the assembly, pressure welding will take place at the cleaned interface and an extremely thin, wide bimetallic strip is produced. The assembly may be pre-heated prior to working in order to increase the tendency for welding and to facilitate the working operation.

In order to prevent welding of the back faces of the metallic strip, and also welding of the material to itself where a single strip provides the scroll 14, the faces of these materials may be oxidized or a layer of weld preventing material may be provided. Other interlayers such as paint, lubricant, certain metals, etc., are contemplated, according to the processing temperature used and other practical considerations.

As an example of the thin sheet that can be processed in accordance with this invention, copper foil having a thickness of .0015 inch was wrapped around a brass rod with a .330 inch outer diameter. The foil was encased in a .500 inch outer diameter copper tube and the assembly was drawn, in four stages, down to a final outer diameter of .345 inch. The core had a final outer diameter of .289 inch, and the foil when separated from the core and case had been reduced to .0010 inch in thickness. The foil was unbroken and no interwelding of the material was apparent.

As a further example, a strip .O01 inch thick and 8 inches wide was integrated with an assembly and given a 90% reduction in assembly cross-section using a relatively soft core. The resulting material was reduced to .0003 inch in thickness and the width of the material was increased to about 24 inches. Similarly, a .04 inch thick, 24 inch wide strip wrapped around a 2 inch diameter hardened steel core and given a drawing reduction of 80% will be decreased in thickness to .008 inch and in creeased to about 120 inches in width.

An additional advantage of the structures of this invention relates to the possibility of working of the material in an evacuated cylinder. Thus, the cylinder-case may be hermetically sealed by evacuating it and closing both ends prior to the working operation. The entire process may then be carried on under vacuum, which can be an extremely important consideration, particularly where readily oxidizable metal is to be heated prior to the working operation.

FIGURE 6 illustrates one possible way of providing for sealing of the assembly of this invention whereby working can be effected under vacuum. In the illustrated assembly, the strip 40 is wrapped around a core 42 and the outer casing 44 is welded as at 46 to seal off the area between the core and the casing. An outlet 4S is provided whereby the air can be removed from the interior of the casing. Sealing of this outlet will be effected once the desired vacuum is achieved. One conceivable manner of sealing comprises melting of the outlet as by means of an acetylene torch. The outlet member may be advantageously associated wtih the casing by rst threading a hole in the casing and then screwing the outlet member into this hole.

The assemblies of this invention are susceptible to many variations insofar as the core and casing materials are concerned. It will be obvious that a softer core will deform to a greater extent for a given reduction than a harder core with the same material wrapped thereabout. A hardened steel core will remain essentially undeformed, while the assembly within which it is contained may be considerably reduced. Therefore, it would be expected that the decrease in thickness of the material will proceed at a less rapid rate when a softer core is employed. Where it is desired to employ a relatively rigid core for maximum reduction, it is necessary that the core be long enough originally to accommodate the elongating scroll at all times.

It will be understood that various modifications may be made in the above described process which provide the characteristics of this invention without departing from the spirit thereof, particularly as defined in the following claims.

I claim:

l. A process for the working of metallic sheet, strip and similar material comprising the steps of wrapping said material about a core, encasing the material wrapped about the core with a cylinder to hold said material in place, and working the assembly to reduce the outer diameter thereof, whereby said material is reduced in thickness and the width thereof is increased.

2. A process according to claim l wherein said working step includes swaging the end of the assembly and drawing the assembly through at least one drawing die.

3. A process according to claim l wherein said working step includes extruding the assembly through at least one extrusion die.

4. A process according to claim 1 including the step of providing a vacuum within the cylinder after encasing said material therein and hermetically sealing said cylinder whereby the working operation may be carried out under a vacuum.

5. A process for reducing the thickness and increasing the width of sheet, strip and similar material comprising the steps of providing a solid core having a length in excess of the width of said material, wrapping said material about said core in a manner such that the width thereof extends along the length of the core, fastening the end of the material to the layer underneath, encasing said material in a cylinder whereby it is loosely fit therein and Working said cylinder so that it will maintain the material in the Wrapped state, further working the assembly made up of said cylinder, material and core whereby the outer diameter thereof is reduced, the thickness of said material is reduced and the width of said material is increased, and removing the cylinder and material from the core.

6. A process according to claim 5 wherein said cylinder is notched prior to the working step to facilitate removal of the cylinder.

7. A process for reducing the thickness and increasing the width of sheet, strip and similar material comprising the steps of providing a solid core having a length somewhat in excess of the width of said material, wrapping said material about said core in a manner such that the width thereof extends along the length of the core, and whereby the core extends beyond the wrapped material,

encasing said material in a cylinder whereby the material is maintained in the wrapped state, said cylinder having a length corresponding to said core and also extending as said core, inserting a deformable ller material in the opening between the core and cylinder where they extend beyond the material, swaging the lled end of the assembly, and drawing the assembly through a drawing die whereby the outer diameter is reduced, the thickness of said material is reduced and the width of said material is increased, and removing the cylinder and material from the core.

8. A process for the working of metallic sheet, strip and similar material comprising the steps of Wrapping said material about a core, encasing said material wrapped about the core with a cylinder to hold said material in place, heating the assembly formed thereby to elevated temperatures to facilitate working, and working the assembly to reduce the outer diameter thereof whereby said material is reduced in thickness and the width thereof is increased.

9. A process for the working of bimetallic sheet, strip and similar material comprising the steps of providing lirst and second strips of dissimilar metals, cleaning one face of each of said strips :and mating said cleaned faces, wrapping the material formed by said mated strips about a core, encasing said material wrapped about the core with a cylinder to hold said material in place and working the assembly to reduce the outer diameter thereof whereby the mated faces are pressure Welded one to the other and said material formed by the first and second strips is reduced -in thickness and the width thereof is increased.

10. A process according to claim 9 including the step of heating the assembly prior to working References Cited in the file of this patent UNITED STATES PATENTS 40,498 Patterson Nov. 3, 1863 796,970 Hoopes Aug. 8, 1905 889,728 Skinner June 2, 1908 2,104,884 Quarnstrom Jan. l1, 1938 2,177,435 Kretz Oct. 24, 1939 2,212,481 Sendzimir Aug. 20, 1940 2,423,810 Goulding July 8, 1947 2,820,751 Sailer Jan. 21, 1958 FOREIGN PATENTS 161,002 Australia Feb. 8, 1955 559,378 Germany Sept. 19, 1932 689,051 Great Britain Mar. 18, 1953 OTHER REFERENCES Randall, R. N,: Fundamental and Applied Research and Development in Metallurgy, Extrusion by Hydrostatic Pressure, Nuclear Metals, Inc., for U.S.A.E.C., July 1961, 34 pages, order NMI-1250 from OTS, U.S. Dept. of Cornmerce, Washington, DC., price 75. 

1. A PROCESS FOR THE WORKING OF METALLIC SHEET, STRIP AND SIMILAR MATERIAL COMPRISING THE STEPS OF WRAPPING SAID MATERIAL ABOUT A CORE, ENCASING THE MATERIAL WRAPPED ABOUT THE CORE WITH A CYLINDER TO HOLD SAID MATERIAL IN PLACE, AND WORKING THE ASSEMBLY TO REDUCE THE OUTER DIAMETER THEREOF, WHEREBY SAID MATERIAL IS REDUCED IN THICKNESS AND THE WIDTH THEREOF IS INCREASED. 